Case-hardening compound.



UNITED STATES PATENT OFFICE ALFRED O. BLAIGH, OF CHICAGO, ILLINOIS.

CASE-HARDENING COMPOUND.

vide an improved'mixture or compound for' easehardening, the basal element of which is'leather.

It consists in the elements characterized and intermixed as hereinafter described as indicated in the claims.

Charred scrap leather constitutes the basal element employed in producing the compound which constitutes this invention. The charred leather is reduced to granular condition by any propermechanical means and intermixed with fromthree to five per.

cent. by weight of sodium salt. The two elements thoroughly intermixed constitute a very effective case-hardening compound; but especially when it is produced by the I method hereinafter. described, which causes the leather to be impregnated with sodium salt, there is preferably comprised in the mixture about ten per cent. by weight of calcium carbonate in addition to the charred leather and sodium salt.

It is suilicient'for the production of a very etl'ective compound that the elements mentioned be thoroughly intermixed mechanically, the charred scrap leather being, as stated, first reduced to granular form. But the most desirable form of the compound is produced by a process which causes the leather to be impregnated with the other elements. This process is as follows:- Scrap leather is intermixed with from three to five per cent. by weight of sodium salt and ten per cent. by weight of calcium car- Specification of Letters Patent.

Application filed October 18, 1913. Serial No. 795,873.

bonate, the three elements being thoroughly stirred together so that every granule or fragment of leather is in the immediate presence of a suitable quantity of the sodium salt and calcium carbonate. The mixture is now in a liquid-sealed retort exposed to a.

temperature sufficient for charring the leather and for fusing the sodium salt. A temperature of from 1400 to 1600 degrees F. is suitable for effecting both the charring of the leather and the fusing of the sodium salt, and the latter when fused seems to act as a vehicle for carrying the calcium car-' bonate into the pores of the leather, which thus becomes impregnated both with the sodium salt and. the calcium carbonate, an excess of the latter usually remaining adherent to the outer surface of the leather granules or fragments, so that the three elements are inseparably united; and thus there is avoided a minor defect of the product, con sisting of a mere mechanical mixture of the said elements, which is that they are liable to become somewhat separated by gravity in the jolting which may happen in handling and transportation prior to use.

1. A case-hardening compound comprising charred leather and a small per cent. of a sodium salt and a small per cent. of calcium carbonate thoroughly intermixed.

A case-hardening compound consisting of charred leather impregnated by an infusion of a small per cent. of a sodium salt and a small per cent. ofcalcium carbonate.

In testimony whereof I have hereunto set my hand, at Chicago, Illinois, this 15th day of October, 1913.

ALFRED O. BLAICH.

lVitnesses CHAS. S. BURTON, LUCY I. STONE. 

